linux-kernel - Re: [PATCH v1] scsi: ufs: Fix ufshcd_scale

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Date:   Fri, 29 Jul 2022 13:11:59 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Stanley Chu <stanley.chu@...iatek.com>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, martin.petersen@...cle.com,
        avri.altman@....com, alim.akhtar@...sung.com, jejb@...ux.ibm.com
Cc:     peter.wang@...iatek.com, chun-hung.wu@...iatek.com,
        alice.chao@...iatek.com, powen.kao@...iatek.com,
        mason.zhang@...iatek.com, qilin.tan@...iatek.com,
        lin.gui@...iatek.com, eddie.huang@...iatek.com,
        tun-yu.yu@...iatek.com, cc.chou@...iatek.com,
        chaotian.jing@...iatek.com, jiajie.hao@...iatek.com
Subject: Re: [PATCH v1] scsi: ufs: Fix ufshcd_scale_clks decision in recovery
 flow

On 7/29/22 00:55, Stanley Chu wrote:
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 581d88af07ab..dc57a7988023 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -1574,8 +1574,6 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>   	ufshcd_rpm_get_sync(hba);
>   	ufshcd_hold(hba, false);
>   
> -	hba->clk_scaling.is_enabled = value;
> -
>   	if (value) {
>   		ufshcd_resume_clkscaling(hba);
>   	} else {
> @@ -1586,6 +1584,8 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
>   					__func__, err);
>   	}
>   
> +	hba->clk_scaling.is_enabled = value;
> +
>   	ufshcd_release(hba);
>   	ufshcd_rpm_put_sync(hba);
>   out:
> @@ -7259,7 +7259,8 @@ static int ufshcd_host_reset_and_restore(struct ufs_hba *hba)
>   	hba->silence_err_logs = false;
>   
>   	/* scale up clocks to max frequency before full reinitialization */
> -	ufshcd_scale_clks(hba, true);
> +	if (ufshcd_is_clkscaling_supported(hba) && hba->clk_scaling.is_enabled)
> +		ufshcd_scale_clks(hba, true);
>   
>   	err = ufshcd_hba_enable(hba);

I see a race condition between the hba->clk_scaling.is_enabled check in 
ufshcd_host_reset_and_restore() and the code that sets 
ufshcd_clkscale_enable_store(). Shouldn't the code in 
ufshcd_host_reset_and_restore() that scales up the clocks be serialized 
against ufshcd_clkscale_enable_store()?

Thanks,

Bart.